package leetcode3;

import leetcode.ListNode;

/**
 * 141. 环形链表
 * 给定一个链表，判断链表中是否 有环。
 * 
 * @author stick
 *
 */
public class HasCycle {

	public boolean hasCycle(ListNode head) {
        if (head == null || head.next == null) {
            return false;
        }
        ListNode slow = head;
        ListNode fast = head.next;
        while (slow != fast) {
            if (fast == null || fast.next == null) {
                return false;
            }
            slow = slow.next;
            fast = fast.next.next;
        }
        return true;

    }
	
}
